1. Technical Field
The present invention relates to an image forming method, which is applicable to a photocopying machine, a printer, a facsimile equipment or the like, and in which an electrostatic latent image is formed on an image support member, and the formed electrostatic latent image is developed with toner, and pictorial image is formed.
2. Description of Related Art
Conventionally, in the copying machine which utilizes an electrophotography process, it is necessary to fix an unfixed toner image formed on the recording sheet to form an eternity image, and a heating roller fixing method conducted by the heating and the pressurization is a general fixing method. That is, a known apparatus is a heating roller type fixing apparatus, which comprises: a heating roller which comprises a heater lamp within a cylindrical core metal and a heat resistant releasing layer formed on the outer surface thereof; and a pressure roller which is disposed in a compressibly contacting manner against this heating roller (fixing roll), and comprises a heat-resistant elastic body layer formed on outer surface of the cylindrical core metal, wherein a fixing process is conducted by applying a constant pressure between both these rollers and inserting therebetween a support member such as normal paper on which an unfixed toner image is formed. Because the heating roller type fixing apparatus used for this system has higher thermal efficiency, in comparison with other heating fixing methods such as a flash fixing system and an oven fixing system, and thus requires lower electric power, provides better processing speed, and also provides lower fire-hazardous nature caused by a paper jam, the heating roller type fixing apparatus is the most popular system at the present time.
However, since the fixing apparatus of the heating roller fixing system using the heating roller (rotating part materials for fixing) requires to heat the heating roller for fixing having larger heat capacity, when transference materials and the toner are heated with the heating roller having halogen heater therein, it is disadvantageous for the energy conservation effect, and thus it provides poor energy conservation, and further, since time consumes for warming up the fixing apparatus in a printing process, there is problem of requiring longer printing time (warming up time).
In recent years, there is a demand for increasing the fixing rate in such heating roller type fixing apparatus, and in order to satisfy the demand, the width of the nip region, or in other words the nip width, is required to be increased. Here, methods for increasing the nip width include a method for increasing the load exerted between these rollers, or a method for increasing roller diameter of both the fixing roller and the pressure roller, or the like. However, there is a limitation in the available fixing rate that can correspond with these methods, and in order to apply for the higher fixing rate region, a heating roller belt type fixing apparatus is developed.
Pressurizing belts employed for the heating roller belt type fixing apparatus as mentioned above may mainly and be classified into two types of belts, in general. More specifically, the belts are classified into:    1) fluorine resin-coated belt, which is formed by coating the base film of endless belt shape with an adhesive referred to as “primer”, and thereafter thinly coating thereof with a fluorine resin such as polytetrafluoroethylene (PTFE) or copolymer of tetrafluoroethylene and perfluoroethylene (PFA) and so on; and    2) silicone rubber coating belt or fluorine-containing rubber coating belt, which is formed by thinly coating the base film having endless belt shape with silicone rubber or fluorine-containing rubber via a primer therebetween.
As the fixing system that employs the metal belt (belt member) having the above mentioned rubber layer, and has an exothermic roller (exothermic roller member), which heats the belt member and provided in the inside of belt member, is disclosed in, for example, JP-Tokukai 2000-267356, JP-Tokukai 2000-60050 and JP-Tokukai 09-138599.
However, the above-mentioned proposed fixing apparatus, which uses endless belt, has a drawback of having lower fixing strength due to its lower fixing load (pressurization) as compared with the heating roller system, and among other things, there are various problems of varying the fixing strength depending on the types of the toner and the transfer paper, and thus it is the present situation that does not reach to apply the fixing apparatus containing this system to the application of a high speed printer and a high speed photocopying machine.
Furthermore, since the above-mentioned fixing system involves heating the toner image, a minor constituent included in the toner is released into the atmosphere, and there is a case, which causes an unpleasant odor for the users. More in recent years, accompanying with the reduction of the size of the photocopying machine and the printer, opportunity of using them with intimacy becomes increasingly in offices. In addition, the opportunity of using such machines in general families have been increased, and as a result, the case, in which odor emitted from the toner gives an unpleasant feeling to the user, increases more often than conventional.